1. Field of the Invention
The present invention relates generally to a dual stage air bag assembly, which acts to reduce the likelihood and/or severity of injury to an occupant when the air bag is inflated and deployed during a collision. More particularly, the invention relates to a dual stage air bag assembly which includes an inner bag member communicating with an outer bag member via a plurality of apertures defining gas discharge outlets. The inner bag member is connected with an inflation mechanism so as to be immediately inflated in its entirety at the time of a collision, while the outer bag member receives gas secondarily in a predetermined flow pattern via the gas discharge outlets in the inner bag member.
2. Description of the Background Art
Air bag devices, for restraining a vehicle occupant in the event of a collision, are well known, and are installed as standard safety equipment in many vehicles. However, a serious problem associated with air bag devices is that when the air bag is automatically inflated and deployed, to restrain an occupant against injury at the time of a collision, the air bag itself may cause injury to the occupant.
Air bag devices are typically designed to inflate rapidly and forcefully, while generally being adapted to effectively restrain an adult driver or passenger of average height and weight in a normal sitting posture. However, for an adult or child of small physical proportions whose sitting posture is unusually low and/or forward in the seat, or for a child fastened in a safety seat, the sudden forceful inflation of a standard air bag may pose a severe and potentially fatal hazard. The forceful inflation of the air bag may cause an impact to such an occupant which itself may cause serious injury, aside from any considerations of other potential injury from a collision.
While attempts have been made to overcome this serious safety hazard associated with conventional air bags, such attempts have proven costly and/or ineffective. One such attempt is an air bag system in which a single air bag is deployed at a relatively slow or fast rate, depending on the user. Another attempt is a level sensor device which is programmed with the occupant""s or user""s height and weight. Previously issued patents relating to air bags and to attempts to moderate the dangers thereof include U.S. Pat. Nos. 3,802,719, 3,814,458, 3,900,210, 4,265,468, 5,018,762, 5,181,697, and 5,468,013.
Some air bag designs include an inner bag disposed within an outer bag to modify the deployment action of the air bag. In most instances, this bag-within-a-bag type of design uses either a stretchable elastic inner bag, or a porous inner bag, which may be formed of a woven or knit material.
U.S. Pat. No. 3,761,111 to Kemper discloses a two-part air bag device which includes a foldable and collapsible outer bag, which is sealed all around and made of a gas-tight material. A foldable and collapsible inner bag, smaller than the outer bag and made of a porous material, is disposed inside the outer bag, so that the smaller, porous inner bag is inflated first.
U.S. Pat. No. 3,900,210 to Lohr et al. discloses an air bag assembly similar to the device of Kemper. In the design of Lohr et al., an inner, energy absorbing elastic bag is disposed inside an outer bag. The inner bag has elastic walls which expand under pressure, and is preferred to be made of a knitted material such as, e.g., nylon or polyester. All inflating material is directed into the inner bag, and must diffuse outwardly therefrom into the outer bag, after the inner bag has expanded significantly (50-100%) beyond its initial inflated but unexpanded volume. The outer bag may also be made of an expandable, knitted material. The energy absorbing action of the inner bag (and perhaps the outer bag) of Lohr is provided to reduce the sound level of the explosion associated with the inflation of the air bag.
Although the bag-within-a-bag design for air bags is superior to the single bag design, the use of materials for the inner bag which acts equally at every section thereof, such as elastic materials or porous woven materials, may not be the best approach. Since an occupant in a front seat of a vehicle is likely to impact the outer surface of the bag exclusively, what is needed is a selectively buffered air bag assembly of a two-stage design, which can be designed to selectively direct outwardly expanding gases within the outer bag.
U.S. Pat. No. 5,249,824 to Swann et al. discloses another design for a two-part air bag. In the air bag design of Swann et al., an outer bag is expansible to a predetermined three-dimensional shape, and an expansible inner bag is disposed inside an internal fluid cavity of the outer bag. Both of the inner and outer bags share a common inlet for inflation thereof. The inner bag of Swann is preferred to be made of a woven synthetic material, such as nylon. The inner bag has a plurality of rearwardly facing reinforced vent openings formed in a rear panel thereof, to direct gas under pressure from the inner bag into the outer bag, in a direction away from an occupant impact area thereof, in order to create a radially swirling flow pattern within the outer bag. The rear surface of the outer bag of Swann is also provided with a plurality of vents, enabling the air bag structure to be deflated in a controlled fashion when the air bag is struck by a vehicle occupant.
However, these and other attempts have not been completely effective at providing a simple, cost effective, reliable, and safe air bag which deploys in a selectively buffered fashion, so as to minimize injury caused by the air bag itself.
The present invention provides a selectively buffered dual stage air bag assembly. The air bag assembly according to the present invention effectively minimizes the danger of injuring passengers during deployment of the air bag, while at the same time ensuring that the occupant will be restrained against injury at the time of a collision. Further, the assembly according to the invention is simplified in structure and relatively inexpensive to produce.
The air bag assembly of the present invention includes an outer bag member, and an inner bag member disposed within the outer bag member. The inner bag member includes an outer wall with an outwardly facing surface for deployed placement facing toward an occupant of a vehicle passenger compartment. The outer wall of the inner bag has a plurality of apertures formed therethrough, which define gas discharge ports for discharging gas from the inner bag member to the outer bag member, in a substantially outward direction, towards the passenger compartment of a vehicle. The material of the inner bag member is preferably reinforced in the area adjacent the apertures, and may, optionally, have a porous material disposed across the apertures to affect the rate of gas flow therethrough. In one embodiment, plastic reinforcing grommets may be provided, attached to the outer layer of the inner bag member to provide reinforcement in the area of the apertures. Preferably, the inner bag member is made from a non-woven, substantially inelastic material, and is constructed of stronger material than the outer bag.
Due to the unique structure and construction of the air bag assembly according to the present invention, the inner bag receives inflating gases directly from an inflating mechanism, such that it is immediately filled to 100% of its volume, thereby providing initial impact resistance for a vehicle occupant, and then the inner bag channels the inflating gases straight outwardly through the apertures in the outer wall thereof and into the outer bag in a predetermined pattern, so that the outer bag is inflated a short time subsequent to the inflation of the inner bag, but still prior to the time that a passenger of the vehicle is likely to contact the air bag assembly.
The present invention further provides a method of using an air bag assembly of the type described.
It is an object of the present invention to minimize danger to vehicle occupants posed by excessively rapid and forceful deployment of vehicle air bags.
It is another object of the present invention to provide a selectively buffered air bag assembly, which will open in two stages to minimize danger of injury to passengers in a vehicle, and which provides selectively buffered gas flow, in a direction towards a vehicle passenger compartment, during inflation of an outer air bag thereof.
Further objects, features, details, and advantages of the invention will become apparent from the following detailed description, when read in conjunction with the accompanying drawings.